#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>

int main()
{
	int f0 = 0;
	int f1 = 1;
	int F = 0;
	int n = 0;
	scanf("%d", &n);
	for (int i = 1; i < n; i++)
	{
		F = f0 + f1;
		f0 = f1;
		f1 = F;
	}
	printf("%d", F);
	return 0;
}